Camshaft adjuster

ABSTRACT

An electrically-actuatable camshaft adjuster includes an adjustment gear which has a drive wheel with an external toothing. The adjustment gear also has an additional ring-shaped component which is solidly screwed to the drive wheel. In particular, the drive wheel has internal threading into which outer threading of the ring-shaped component is screwed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Phase of PCT/DE2016/200414 filedSep. 2, 2016, which claims priority to DE 102015217292.9 filed Sep. 10,2015, the entire disclosures of which are incorporated by referenceherein.

TECHNICAL FIELD

This disclosure relates to a camshaft adjuster suitable for an internalcombustion engine, which has an adjustment gearing.

BACKGROUND

A generic camshaft adjuster is known, for example, from EP 1 718 846 B1.This camshaft adjuster can be actuated electrically, and has athree-stage planetary gearing, specifically a planetary gearing thatfunctions as an adjustment gearing. A drive wheel of the camshaftadjuster is screwed to a stop ring. Rivet attachments, welding, andcaulking are given as alternative attachment methods in EP 1 718 846 B1.

Further constructions of electrically actuatable camshaft adjusters areknown, for example, from DE 102 48 355 A1. A brushless direct currentmotor with a permanent magnet rotor is provided as the electrical drivetherein.

A combination camshaft adjuster and compensating shaft in an internalcombustion engine is known from U.S. Pat. No. 5,327,859 A. A genericcamshaft adjuster is described, by way of example, in WO 2006/074 732A1. EP 0 902 169 B1 describes a further camshaft adjuster.

An object of this disclosure is to further develop a camshaft adjusterfor an internal combustion engine that has an adjustment gearing thatcan be actuated electrically, in particular regarding a beneficialconstruction with regard to installation.

SUMMARY

This problem is solved in accordance with embodiments of the disclosureincluding a camshaft adjuster described herein.

The camshaft adjuster comprises an adjustment gearing, which has a drivegear with an outer toothing, and a further annular component can besecurely screwed to the drive gear. In accordance with this disclosure,the drive gear has an internal threading that is concentric to its axisof rotation, into which an outer threading of the further annularcomponent is screwed. The camshaft adjuster may be actuatedelectrically, but it can, however, be actuated in theory by other means,in particular hydraulically.

The further annular component, which is securely screwed onto the drivewheel that has an external toothing, is a drive ring gear with an innertoothing in an exemplary design, and may have an integral design. Thisdrive ring gear functions in particular as a component of a planetarygearing provided as an adjustment gearing, i.e. a three-stage planetarygearing.

In contrast to known solutions, the drive ring gear according to oneembodiment is screwed to the drive gear, in particular a chain wheel, bymeans of a single screw. This construction allows for a quick andprecise installation. There is no need for a front cover on the assemblycomprising the drive gear and further annular components. The mechanicaltensions and axial deformations are significantly reduced in comparisonwith assemblies that have numerous screws. In addition to theinstallation, preparation steps for the drive gear are also simplifiedin that, in particular, there is no longer any need to create numerousthreaded holes. Through the elimination of individual threaded holesdistributed on the circumference, the assembly comprising the drive gearand further annular components is particularly robust with respect tocrack formation occurring at the screwing points, wherein the drive gearis particularly suited for heat treatment processes, in particularinductive tempering.

In an advantageous design, the further annular component screwed intothe drive gear, e.g. the drive ring gear, has an actuation contour for atool on its circumference, which extends radially over a circumferentialsurface of the drive gear. The surface of the drive gear (e.g., thecylindrical circumferential surface) lies radially inside the outertoothing of the drive gear. Likewise, the actuation contour formed onthe further annular component may be disposed inside the outer toothingof the drive gear. The actuation contour thus lies—with respect to thecentral axis of the drive gear and the further annularcomponent—radially between the cylindrical circumferential surface andthe outer threading of the drive gear. The drive gear can be used todrive the camshaft using a tensioning device, or to drive the camshaftvia gear teeth, in particular by means of an upright shaft.

According to an embodiment, the further annular component, e.g. thedrive ring gear, has a centering contour that corresponds to a hole inthe drive gear. It is thus possible to securely screw the furtherannular component to the drive gear and to center it in relation to thedrive gear in a single work step. The centering contours of the furtherannular component and the drive gear may be disposed axially between aflange and the outer threading on the further annular component.

There may be at least one plane perpendicular to the central axis of theadjustment gearing and thus to the central axis of the drive gear, whichintersects both the cylindrical circumferential surface as well as thecentering contour of the drive gear. The entire camshaft adjuster isthus particularly compact, in particular in the axial direction of thecamshaft.

Additional securement may be provided to ensure a secure screwconnection. As a result, the screw connection can no longer be loosenedor released by high alternating torques that may occur during operationof the camshaft adjuster. By way of example, the threading may becomecompressed when screwed together, such that the screw connection can nolonger be released. Alternatively or additionally, the drive ring gearand the drive gear may have end walls that are axially adjacent to oneanother and have a surface structure that increases friction or providesan additional form fit through the edges thereof.

Separate screws may be needed for the screwing, because the screwconnection is formed solely by the drive ring gear and the drive gearcomponents. The drive gear may be screwed directly to the drive ringgear. The drive gear and drive ring gear may have an integral design forthis.

Numerous windings of the screw connection are necessary for a securescrewing. At least four windings may be provided for.

The screw connection may be disposed on the side of the drive gearfacing away from the camshaft with respect to the outer toothing. Theinstallation can thus take place in a simple manner at the end, wherethere is sufficient space and engagement surface for a tool. In afurther development, the drive gear has an axial stop for the drive ringgear.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment shall be described in greater detail below onthe basis of the drawings. Therein:

FIG. 1 shows a camshaft adjuster that can be actuated electrically, in asimplified sectional view, and

FIG. 2 shows a drive gear of the camshaft adjuster according to FIG. 1in a perspective view.

DETAILED DESCRIPTION OF THE DRAWINGS

An electric camshaft adjuster for an internal combustion engine, e.g. adiesel or gasoline engine, indicated on the whole with the referencesymbol 1, has a chain wheel serving as the drive gear 2, and an outputdrive gear 3 that is concentric thereto, which is securely connected toa camshaft 4. When the internal combustion engine is in operation, thecamshaft 4 rotates, as long as the camshaft adjuster 1 is not actuated,at one half of the rotational rate of the crankshaft of the internalcombustion engine. The camshaft adjuster 1 may be used for adjusting thetiming of the intake and exhaust valves of the internal combustionengine. With regard to the principle functions of the camshaft adjuster1, reference is made to the prior art cited in the introductory portionof the description. Because the camshaft adjuster 1 is electric, it canbe adjusted not only when the internal combustion engine is inoperation, but also prior to start-up.

An adjustment gearing 5, specifically a planetary gearing in the form ofa three-stage planetary gearing, is merely indicated in FIG. 1. Therotation of the shaft of an electric motor, not shown, is introduced viaan Oldham disk 6 into the adjustment gearing 5 of the camshaft adjuster1. The Oldham disk 6 is a component of an Oldham coupling, e.g. acompensating coupling, which allows for a radial offset between an inputdrive shaft and an output drive shaft. As long as the shaft of theelectric motor, and thus the Oldham disk 6, rotates at the same rate asthe camshaft 4, there are no phase shifts between the crankshaft (notshown) and the camshaft 4 of the internal combustion engine. Such phaseshifts only occur when the shaft of the electric motor that functions asan adjustment shaft for the camshaft adjuster 1, rotates at a differentrate than the camshaft 4, wherein the adjustment gearing 5 is configuredas a reduction gearing.

The annular drive gear 2 has an outer toothing 7, by means of which thedrive gear 2 can be driven using a tensioning device, for example achain. A centering contour 9 in the form of a hole and an innerthreading 8 are located—behind one another axially—on the innercircumference of the drive gear 2. The centering contour 9 extends overa shorter region than the inner threading 8 in the axial directionthereby.

The inner threading 8 corresponds to an outer threading 10 on a furtherannular component 11, specifically a drive ring gear, which is connectedto the drive gear 2 for conjoint rotation therewith. The drive ring gear11 has a substantially sleeve-like shape, wherein there is a flange 12on the end surface of the drive ring gear 11 facing away from thecamshaft 4, which is an integral component of the drive ring gear 11.The diverse gearing components, disposed radially inside the drive ringgear 11, are merely indicated in FIG. 1 by a multi-part drive element13. Individual components of the drive element 13 are connected to oneanother with contact pressure surfaces 14, 15.

In order to screw the drive ring gear 11 into the drive gear 2, anactuation contour 16, e.g. in the form of a hexagonal contour, isprovided on the flange 12 of the drive ring gear 11, and the drive gear2 and the drive ring gear 11 can be screwed together with a tool, notshown. At the same time, the centering contour 9 of the drive gear 2, inthe form of a hole, together with a corresponding centering contour ofthe drive ring gear 11, ensures a precise coaxial positioning of thedrive gear 2 and the drive ring gear 11. The drive gear 2, which is achain wheel, has an integral design, and is inductively tempered, atleast on parts of its surface.

The actuation contour 16 of the drive ring gear 11 is disposed radiallyoutside a cylindrical circumferential surface of the drive gear 2,indicated by the numeral 18, and radially inside the outer toothing 7 ofthe drive gear 2. A single plane, perpendicular to the rotational axisof the camshaft 4 indicated by the letter A, i.e. the central axis ofthe adjustment gearing 5, intersects both the actuation contour 16 ofthe drive ring gear 11, as well as the Oldham disk 6, such that theOldham coupling can be accommodated in a space saving manner, partiallyengaging in the adjustment gearing 5.

A further plane, parallel to the specified plane, intersects both thecylindrical circumferential surface 18 as well as the centering contour9 of the drive gear 2. A radial bearing 17, in the form of a slidingbearing, is located radially inside the outer toothing 7 of the drivegear 2, and the drive element 13, in the form of an output drive gear,is supported in the drive gear 2.

As a result of the overall compact construction of the camshaft adjuster1, undesired torques are introduced into the adjustment gearing 5 onlyto a very limited extent during operation thereof. The inner threading 8as well as the outer threading 10 of the drive ring gear 11 interactingtherewith, are oriented such that the screw connection between theseparts 2, 11 is tightened when the internal combustion engine is inoperation, i.e. when the camshaft 4 is driven.

LIST OF REFERENCE SYMBOLS

-   1 camshaft adjuster-   2 drive gear-   3 output drive gear-   4 camshaft-   5 adjustment gearing-   6 Oldham disk-   7 outer toothing-   8 inner threading of the drive gear-   9 centering contour of the drive gear, hole-   10 outer threading of the drive ring gear-   11 further annular component, drive ring gear-   12 flange-   13 output drive element-   14 contact pressure surface-   15 contact pressure surface-   16 actuation contour-   17 radial bearing-   18 cylindrical circumferential surface-   A axis of rotation

The invention claimed is:
 1. A camshaft adjuster that has an adjustmentgearing, comprising a drive gear with an outer toothing configured to bedriven by a tensioning device, and a further annular component securelyscrewed thereto, wherein the drive gear has an inner threadingconcentric to its axis of rotation, into which an outer threading of thefurther annular component is screwed; wherein the further annularcomponent is a drive ring gear with an inner toothing; wherein thefurther annular component has a centering contour corresponding to acentral hole of the drive gear; and wherein the central hole is disposedbetween a flange and the outer threading of the drive ring gear.
 2. Thecamshaft adjuster according to claim 1, wherein the adjustment gearingincludes a planetary gearing, and the drive ring gear is a component ofthe planetary gearing.
 3. The camshaft adjuster according to claim 1,wherein the further annular component has an actuation contour on itscircumference for a tool, the actuation contour extending radially overa circumferential surface of the drive gear.
 4. The camshaft adjusteraccording to claim 3, wherein the actuation contour is disposed radiallyinside the outer toothing of the drive gear.
 5. The camshaft adjusteraccording to claim 1, wherein there is a plane that is perpendicular toa central axis (A) of the adjustment gearing, which intersects both acylindrical circumferential surface of the drive gear as well as thecentering contour of the drive gear.
 6. The camshaft adjuster accordingto claim 1, wherein the screw connection of the inner threading and theouter threading is reinforced by additional securing structure.
 7. Acamshaft adjuster comprising: adjustment gearing configured to rotateabout a central axis; a drive gear having outer toothing configured tobe driven by a tensioning device, and an inner-facing surface facingtoward the central axis, the inner-facing surface defining innerthreading, and the drive gear defining a central hole; and a drive ringgear coupled to the adjustment gearing and having an outer-facingsurface facing away from the central axis, the outer-facing surfacedefining outer threading mating with the inner threading such that thedrive gear and the drive ring gear are coupled together via a screwingengagement, wherein the drive ring gear includes a centering contourcorresponding to the central hole, wherein the central hole is disposedbetween a flange and the outer threading of the drive ring gear.
 8. Thecamshaft adjuster of claim 7, wherein the adjustment gearing includesplanetary gearing.
 9. The camshaft adjuster of claim 7, wherein thedrive ring gear defines a circumference having an actuation contourconfigured to receive a tool, the actuation contour is radially outwardof a circumferential surface of the drive gear.
 10. The camshaftadjuster of claim 9, wherein the actuation contour is radially inward ofthe outer toothing of the drive gear.
 11. A camshaft adjustercomprising: a drive gear having an outer surface configured to be drivenby a chain, and an inner-facing surface defining inner threading, thedrive gear defining a central hole; planetary gearing including, anouter drive ring gear, the drive ring gear having an outer-facingsurface defining outer threading mating with the inner threading suchthat the drive gear and the drive ring gear are coupled together via ascrewing engagement, wherein the drive ring gear includes a centeringcontour corresponding to the central hole, wherein the central hole isdisposed between a flange and the outer threading of the drive ringgear.